Rock drill rotation mechanism



0a. 12, 1965 w. D. FISH 3,211,021

ROCK DRILL ROTATION MECHANISM Filed May 13, 1964 INVENTOR. WALTER D. FISH H/S ATTORNEY United States Patent 3,211,021 ROCK DRILL ROTATION MECHANISM Walter D. Fish, Claremont, NJBL, assignor to Joy Manufacturing Company, Pittsburgh, Pa, a corporation of Pennsylvania Filed May 13, 1964, Ser. No. 367,038 2 Uaims. (Cl. 74577) This invention relates to a rock drill rotation mechanism and more particularly to a rotation mechanism for a hammer rock drill whereby a drill steel is rotated intermittently by the hammer piston.

The present invention provides an improved ratchet to be used in a rifle bar rotation mechanism such as that disclosed in US. Patent No. 3,074,381, Osgood, entitled Rock Drill Rotation Mechanism.

In rifle bar rotation mechanism it is well known to provide a ratchet comprising a plurality of pawl members engageable with a ring of notches or teeth so that the rifle bar is free to rotate in one direction and prevented from rotating in the opposite direction. The pawls and notches of prior art devices are provided with planar surfaces of engagement which surfaces provide area contact for only a single position of engagement. Other positions of engagement of the pawl and notch in a prior art device result in line contact rather than bringing an area of surface into engagement. The pawls and teeth of the present invention are provided with arcuate surfaces which upon engagement provide area contact in varied pawl positions.

It is therefore an object of this invention to provide a new and improved rock drill rotation mechanism.

It is another object of this invention to provide a new and improved rock drill rotation mechanism having novel ratchet pawls and teeth.

It is a further object of this invention to provide a new and improved rock drill mechanism wherein a ratchet mechanism is provided with an arcuate engagement surface on a pawl engageable with a similarly .arcuate engagement surface on any one tooth of a series of teeth.

It is yet another object of this invention to provide a ratchet mechanism wherein the respective engagement surfaces of a pawl and a series of teeth are arcuate in nature to provide area contact between the pawl and a respective tooth in a variety of pawl positions.

These and other objects and advantages of the present invention will be more readily understood by referring to the following description and drawings in which:

FIGURE 1 is a sectional view taken on a plane normal to the axis of a rifle bar rotation mechanism and showing a plurality of pawls and teeth constructed according to the principles of this invention;

FIGURE 2 is an enlarged fragmentary view of a portion of the ratchet mechanism of FIGURE 1; and

FIGURE 3 is a sectional view similar to FIGURE 1 showing, in reduced scale, a second embodiment of the ratchet mechanism of this invention.

In FIGURE 1 there is shown a ratchet mechanism constructed according to the principles of this invention and comprising a hollow cylindrical ratchet ring 12 to be mounted in the body of a percussive rock drill of the type shown and described in the above cited patent. The ratchet ring 12 surrounds and is coaxial with a radially enlarged head portion 14 of an elongated, spirally splined, rifle bar (not shown) such as that shown in the above cited patent. The ratchet ring 12 has an inner peripheral surface 15 and an outer peripheral surface 16 and is provided with a plurality (shown as four) of bores 18 extending from the outer periphery 16 through the inner periphery 15, all of which bores 18 have their axes in a common plane normal to the axis of the ratchet ring 12. Each of the bores 18 is provided with a hollow cylindrical plunger 20 having a substantially conical closed inward end 21 each plunger 20 being biased inwardly of the periphery 15 by a spring 22 of the hollow cylindrical compression type partially compressed between the plunger 20 and a spring stop element 23 rigidly secured in the outer end of each bore 18 as by welding. Axially offset from, but breaking into each bore 18 at its inner end is a partial bore 24 which also breaks into the space within the inner periphery 15 and has an axis parallel to the axis of the ratchet ring 12. Each bore 24 provides a pivotable mounting for a generally rectangular pawl member 26 having a partially cylindrical head portion 27 mated with the interior surface of the partial bore 24 and coaxial therewith. The rectangular portion of the pawl member 26 is in contact with the conical inward end 21 of the plunger 20 at some distance from the axis of the head portion 27 so that an end portion 28 of the pawl member 26 is biased inwardly away from the inner periphery 15. The end portion 28 is a partially cylindrical surface coaxial with the head portion 27 for a purpose to be described.

The radially enlarged head portion 14 of the rifle bar is provided with a plurality of tooth elements 30 each tooth 30 having a generally flat counterclockwise facing surface 31 suitably slanted for biasing the pawl member 26 outwardly as the head portion 14 rotates in a counterclockwise direction as seen in FIGURE 1. Each tooth member 30 also has a clockwise facing surface 32 which is a partially cylindrical surface having the same radial dimension as the partially cylindrical surface 28 and oriented so that when a particular tooth member 30 is in position to be engaged by the pawl member 26 in response to a force tending to rotate the head portion 14 in a clockwise direction as seen in FIGURE 1, the surface 32 is coaxial with the end portion 28 so that the surface of portion 28 coincides with the surface 32 in that position of the head position 14 and provides for an area of contact substantially equal to the area of the end portion 28. In FIGURE 2 the solid line drawing of the pawl member 26 is shown in such full area contact with one of the surfaces 32 while a dot and dash representation of an end portion of the pawl member 26 shows the effect of a partial engagement of the pawl member 26 with a tooth 30 wherein something less than half of the surface 32 is engaged by the end portion 28. It is to be noted, however, that with such partial engagement there is still an area of contact between the end portion 28 and the surface 32 provided by the coaxial relationship of the surfaces 28 and 32 as distinguished from the line contact which would be developed between two planar surfaces used in place of the surfaces 28 and 32 as in devices of the prior art whenever less than full tooth engagement occurs.

Operation of the ratchet mechanism 10 of this invention is the same as that described in my Patent 2,922,396 except for the above described area engagement and will be described in the same terms as used in that patent. When the hammer piston (not shown) moves forwardly to strike its blow on a steel shank the right-hand twist of the splines of the rifle bar tends to rotate the rifle bar and its head portion 14 in a counterclockwise direction as seen in FIGURE 1. The surfaces 31 bias the pawl members 26 outwardly toward the periphery 15 and cause the teeth 30 to rotate freely in a counterclockwise direction. During rearward motion of the hammer piston the twist of the spline tends to rotate the head portion 14 in a clockwise direction and brings the end portion 28 into contact with one of the surfaces 32 and anchors the head portion 14 and consequently the remainder of the rifle bar so that rotation is then imparted to the piston and consequently to the drill steel as is desired.

The embodiment of FIGURE 3 is entirely similar to that of FIGURES 1 and 2 excepting only that the pawl members 26 and the plungers 20 are mounted in the radially extended head portion 14' of the rifle bar while the teeth 30 are formed on the inner periphery of the ratchet ring 12 in distinction to the relative positioning of the pawl members 26 and the teeth 30 in the embodiment of FIGURES 1 and 2. The teeth 30 and the pawl members 26 have the same engaging portions 28 and 32 in both embodiments. It is to be noted that the principles of this invention can be applied in different types of ratchet mechanism and are not limited to the exact conformation hereinabove described. It is especially to be noted that the end portion 28 and the clockwise facing surface 32 are not necessarily exactly coaxial in all embodiments but can be varied from the coaxial condition to some extent without departing from the principles of this invention.

The advantages of this invention reside in providing arcuate surfaces analogous to the end portion 28 and the clockwise facing surface 32 which are so related as to have area contact whether or not full tooth engagement is achieved.

As shown in the embodiments of this invention such area contact makes it reasonable to use an odd number of teeth 30 (shown as 27) with an even number of pawl members 26 (shown as four) so that only one of the pawl members 26 is engaged with a tooth 30 at any one time. A close inspection of FIGURE 1 will show that any rotation of one-quarter of a tooth will bring one of the pawls 26 into position to engage a tooth and that therefore the twenty-seven teeth of the head portion 14 have a total of 108 engagement positions. In distinction to this ability of the ratchet mechanism 10, the ratchet mechanism of the above cited Osgood Patent 3,074,381 shows all four of the pawl members simultaneously engageable with teeth of the ratchet ring. As a consequence of this multiple engagement the number of possible engagement positions for the rifle bar is equal only to the number of teeth in the ring. As is known, the piston is stationary at the end of the forward stroke and acelerates very rapidly when it begins to move rearwardly. If a large number of engagement positions is available such engagement will occur before the piston has accelerated to a high velocity since the amount of rotation of the rifle bar is proportional to the distance moved by the piston before the ratchet engages. Slower speed engagement reduces the tendency of the pawl member to rebound after initially engaging a tooth and consequently reduces the likelihood of partial tooth engagement. Thus, the large number of engagement positions afforded by the ratchet mechanism is highly advantageous.

It is to be appreciated that the area contact of the pawl members 26 of this invention allows the use of a single pawl to anchor the rifle bar against clockwise rotation without any tendency to cause permanent deformation or work hardening of the engaged surfaces 32 and 28 with consequent failure of the material as would be likely in a device of the prior art with only line contact between the surfaces analogous to end portion 28 and clockwise facing surface 32 whenever full tooth engagement was not achieved. With the ratchet and pawl of this invention the designer is free to make a choice between relatively large teeth and pawl members engageable one at a time as shown in FIGURE 1 or relatively small teeth and pawl members having a plurality of teeth engageable simultaneously, but much smaller than similar teeth required in ratchet mechanisms of the prior art.

It is to be realized that, although the embodiment of the ratchet mechanism of this invention has been described as part of a rock drill, the principles of this invention are equally applicable in other environments where ratchet action is needed.

A particular embodiment of this invention having been described and illustrated, it is to be realized that variations in design can be made without departing from the spirit and scope of this invention. It is therefore respectfully requested that the claims of this invention be interpreted as broadly as possible and be limited only by the prior art.

I claim:

1. A hammer rock drill ratchet mechanism, comprising: a ratchet ring; a given number more than one of pawl members pivotably mounted within and supported by said ratchet ring; a generally cylindrical member coaxial with and rotatable within said ratchet ring; a number, not a multiple of said given number, of tooth members formed on the periphery of said cylindrical member, each tooth member having a concave partially cylindrical face individually engageable with any one of said pawl members; an engagement surface which is a convex partial cylinder on each of said pawl members; each of said tooth member faces having a radius of curvature equal to the radius of curvature of said pawl member engagement surfaces so that when one of said pawl members is engaged with one of said tooth members the respective engagement surfaces thereof are substantially coaxial.

2. A rock drill ratchet mechanism comprising: a plurality of pivotably mounted pawl members; a series of tooth members spaced a given distance apart and having respective faces individually engageable with any one of said pawl members; a convex partially cylindrical engagement surface on each of said pawl members; a concave partially cylindrical engagement surface on said face of each of said tooth members, said tooth member engagement surfaces having the same radius of curvature respectively as said pawl member engagement surfaces and said pawl members being spaced apart a distance not a multiple of said given distance.

References Cited by the Examiner UNITED STATES PATENTS 1,867,929 7/32 Smith 74-l27 1,988,445 1/35 Dovell 74-127 2,224,860 12/40 Curtis 74-127 X 2,366,912 1/45 Lauper.

3,055,441 9/62 Morrison 74--127 X BROUGHTON G. DURHAM, Primary Examiner. 

1. A HAMMER ROCK DRILL RATCHET MECHANISM, COMPRISING: A RATCHET RING; A GIVEN NUMBER MORE THAN ONE OF PAWL MEMBERS PIVOTABLY MOUNTED WITHIN AND SUPPORTED BY SAID RATCHET RING; A GENERALLY CYLINDRICAL MEMBER COAXIAL WITH AND ROTATABLE WITHIN SAID RATCHET RING; A NUMBER, NOT A MULTIPLE OF SAID GIVEN NUMBER, OF TOOTH MEMBERS FORMED ON THE PERIPHERY OF SAID CYLINDRICAL MEMBER, EACH TOOTH MEMBER HAVING A CONCAVE PARTIALLY CYLINDRICAL FACE INDIVIDUALLY ENGAGEABLE WITH ANY ONE OF SAID PAWL MEMBERS; AN ENGAGEMENT SURFACE WHICH IS A CONVEX PARTIAL CYLINDER ON EACH OF SAID PAWL MEMBERS; EACH OF SAID TOOTH MEMBER FACES HAVING A RADIUS OF CURVATURE EQUAL TO THE RADIUS OF CURVATURE OF SAID PAWL MEMBER ENGAGEMENT SURFACES SO THAT WHEN ONE OF SAID PAWL MEMBERS IS ENGAGED WITH ONE OF SAID TOOTH MEMBERS THE RESPECTIVE ENGAGEMENT SURFACES THEREOF ARE SUBSTANTIALLY COAXIAL. 